This thesis presents the results of research into the potential of underground mining methods applicable to inclined thick seams (thickness greater than 3.5m, and seam dip of 15 - 35 degree) in the Quangninh coalfield, Vietnam. The primary objectives of this research are to investigate the most suitable underground methods applicable to inclined thick seams in the Quangninh coalfield and to improve understanding of the operational and geotechnical issues associated with the application of chosen methods in thick seams with steeply dipping conditions. From a risk and operational assessment, the Longwall Top Coal Caving (LTCC) method is considered most appropriate for inclined thick seams under the current mining conditions in Vietnam. The LTCC method offers great potential for the efficient extraction of thick seams by caving coal from the upper section during the mining of the lower section. This significantly reduces the development cost per tonne. Compared to High reach Single Pass Longwalling, the LTCC method offers a low extraction height, resulting in smaller and less expensive equipment and better face conditions. Results from this study identified that for extracting an inclined thick seam, the face retreating along the strike has better operational advantages and better cavability than the face retreating updip or downdip of the seam. The operational issues of the LTCC method when extracting inclined seams are: the stability of the support, transport in the mine, and the difficulties in roof control at the transition between face ends and the gateroads. In terms of geotechnical issues, better cavability of the top coal is anticipated for flat coal seams compared to inclined seams. In addition, the chain pillar for flat coal seams is subjected to a higher vertical stress distribution than that of inclined ones. An improved cavability assessment method for the categorisation of the cavability of the top coal with four categories, ranging from 1 (excellent cavability) to 4 (very poor cavability), was suggested to assist the feasibility and design stages of the LTCC application. The cavability assessment method was conducted by numerical analysis combined with back analysis from the database obtained from past LTCC practices.

Thesis (M.S.)--West Virginia University, 2000. / Title from document title page. Document formatted into pages; contains xii, 140 p. : ill. (some col.), maps (some col.). Includes abstract. Includes bibliographical references (p. 120-122).

Thesis (M.S.)--West Virginia University, 2005. / Title from document title page. Document formatted into pages; contains xi, 65 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 63-64).

Devido ao esgotamento de jazidas economicamente lavráveis a céu aberto, migrou-se para a lavra subterrânea. Porém, como isso é uma prática antiga, alguns métodos de lavra subterrânea deixaram de ser economicamente viáveis devido ao aprofundamento da lavra. Um exemplo disso é a lavra de carvão no sul do Brasil, onde jazidas exploradas a céu aberto ou mesmo pelo método de Câmaras e Pilares, começam a vislumbrar seu exaurimento técnico de lavra, por altos custos e baixa produtividade, o que norteia a busca por alternativas econômicas mais lucrativas. Uma destas alternativas é o método Longwall, praticamente desconhecido no Brasil, porém com crescente e não nova intenção de implementação no país. Isso já se refletiu em tentativas de operações e em novos estudos conceituais de viabilidade para o estado do Rio Grande do Sul. Estes fatores justificaram este estudo que teve por objetivo lançar luz sobre a lavra de carvão pelo método de Longwall, de modo a respaldar a sua implementação no Brasil. Sendo assim, o método foi descrito com enfoque em seus principais pontos, tais como, geomecânica e planejamento; além de apresentar estudos conceituais de lavra em dois cenários. O primeiro projeto conceitual apresenta um cenário tradicional objetivando implementação no Rio Grande do Sul; o segundo, tem por objetivo apresentar relativa flexibilidade do método, adaptando-o a um cenário não tradicional. Concluiu-se com este trabalho que fatores como geomecânica e correto planejamento de lavra são imprescindíveis para o sucesso da implementação do método. A partir dos resultados do estudo conceitual I e da versatilidade proposta no estudo II se justifica o aprofundamento nos estudos de operações por Longwall no país. / Due to the exhaustion of economically mining deposits, migrated to the underground mining. However, as this is an ancient practice, some underground mining methods are no longer economically viable due to the deepening of the mining. An example of this is the mining of coal in southern Brazil, where deposits exploited opencast or even by the Room and Pillars, begin to envision your fatigue, mining technical high costs and low productivity, which guides the search for more profitable economic alternatives. One of these alternatives is the Longwall method, virtually unknown in Brazil, but with growing and not new intention of implementation in the country. It already was reflected in attempts to operations and on new conceptual studies of feasibility for the state of Rio Grande do Sul. These factors justify this study that aimed to shed light on the mining of coal by Longwall method, in order to support its implementation in Brazil. Therefore, the method has been described with focus on its key points, such as, geomechanics and planning; In addition to presenting conceptual studies of raging in two scenarios. The first conceptual design features a traditional setting with the objective of implementation in the Rio Grande do Sul; the second aims to introduce on the flexibility method, adapting it to a non-traditional setting. This work concluded that factors like geomechanics and correct planning of mining are indispensable for the successful implementation of the method. From the results of the study and conceptual versatility proposal in study II justification the deepening in the studies of Longwall operations in the country.

Devido ao esgotamento de jazidas economicamente lavráveis a céu aberto, migrou-se para a lavra subterrânea. Porém, como isso é uma prática antiga, alguns métodos de lavra subterrânea deixaram de ser economicamente viáveis devido ao aprofundamento da lavra. Um exemplo disso é a lavra de carvão no sul do Brasil, onde jazidas exploradas a céu aberto ou mesmo pelo método de Câmaras e Pilares, começam a vislumbrar seu exaurimento técnico de lavra, por altos custos e baixa produtividade, o que norteia a busca por alternativas econômicas mais lucrativas. Uma destas alternativas é o método Longwall, praticamente desconhecido no Brasil, porém com crescente e não nova intenção de implementação no país. Isso já se refletiu em tentativas de operações e em novos estudos conceituais de viabilidade para o estado do Rio Grande do Sul. Estes fatores justificaram este estudo que teve por objetivo lançar luz sobre a lavra de carvão pelo método de Longwall, de modo a respaldar a sua implementação no Brasil. Sendo assim, o método foi descrito com enfoque em seus principais pontos, tais como, geomecânica e planejamento; além de apresentar estudos conceituais de lavra em dois cenários. O primeiro projeto conceitual apresenta um cenário tradicional objetivando implementação no Rio Grande do Sul; o segundo, tem por objetivo apresentar relativa flexibilidade do método, adaptando-o a um cenário não tradicional. Concluiu-se com este trabalho que fatores como geomecânica e correto planejamento de lavra são imprescindíveis para o sucesso da implementação do método. A partir dos resultados do estudo conceitual I e da versatilidade proposta no estudo II se justifica o aprofundamento nos estudos de operações por Longwall no país. / Due to the exhaustion of economically mining deposits, migrated to the underground mining. However, as this is an ancient practice, some underground mining methods are no longer economically viable due to the deepening of the mining. An example of this is the mining of coal in southern Brazil, where deposits exploited opencast or even by the Room and Pillars, begin to envision your fatigue, mining technical high costs and low productivity, which guides the search for more profitable economic alternatives. One of these alternatives is the Longwall method, virtually unknown in Brazil, but with growing and not new intention of implementation in the country. It already was reflected in attempts to operations and on new conceptual studies of feasibility for the state of Rio Grande do Sul. These factors justify this study that aimed to shed light on the mining of coal by Longwall method, in order to support its implementation in Brazil. Therefore, the method has been described with focus on its key points, such as, geomechanics and planning; In addition to presenting conceptual studies of raging in two scenarios. The first conceptual design features a traditional setting with the objective of implementation in the Rio Grande do Sul; the second aims to introduce on the flexibility method, adapting it to a non-traditional setting. This work concluded that factors like geomechanics and correct planning of mining are indispensable for the successful implementation of the method. From the results of the study and conceptual versatility proposal in study II justification the deepening in the studies of Longwall operations in the country.

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Spontaneous combustion occurring in inaccessible areas of underground coal mines is often intractable. Even though routine inspection and/or continuous monitoring help detect the incubation of spontaneous heatings, they may not be able to identify the locations with accuracy. Moreover, implementation of remedial measures is difficult. A new approach to ventilation system design to overcome the problem is investigated in this dissertation. Ventilation layouts are analyzed to identify potential problem areas and nullify the probability of fire occurrence. The focus is directed to longwall gobs. The changing gob characteristics, especially the varying degree of consolidation at different parts of a gob as the face moves, is considered. Analytical studies and computer modeling show that bleederless ventilation in retreating panels is promising. The W -system of ventilation is most suitable. However, there may be difficulties in maintaining the middle entry in a Wsystem / Ph. D.

Photogrammetry and laser scanning are remote sensing technologies with the potential to monitor movements of rock masses and their support systems in underground mine environments. Displacements underground are traditionally measured through point measurement devices, such as extensometers. These are generally restricted to measuring one dimension, may change behavior with installation, may obstruct mining operations, and are restricted to monitoring the behavior of a small area. Photogrammetry and laser scanning offer the ability to monitor rock mass movements at millions of points in a local area, both accurately and quickly. An improved, or augmented, method for measuring displacements underground in a practical, cost-effective manner will lead to an improved understanding of rock mass behavior. Several experiments were performed that demonstrate the applicability of these remote sensing techniques to monitoring rock mass changes. An underground mining environment presents unique challenges to using these tools for monitoring rock movements, such as: poor lighting, dust, fog, and unfavorable geometries. It is important, therefore, to demonstrate that these tools which have applications in other industries, can also be adapted to the conditions of an underground mine. The study sites chosen include two different underground limestone mines, two different underground coal mines, and the Mine Roof Simulator (MRS) at the Pittsburgh Office of Mine Safety and Health Research. Both photogrammetry and laser scanning were tested at different limestone mines to detect scaling and spalling on ribs that occurred over several weeks. Both methods were successfully used to reconstruct three-dimensional models of the limestone ribs and detect areas of rock change between visits. By comparing the reconstructed point clouds, and the triangulated meshes created from them, volumes of rock change could be quantified. The laser scanned limestone mine showed a volume of 2.3 m3 and 2.6 m3 being displaced across two ribs between visits. The photogrammetry study involved seven different pillars and at least one rib face modeled on each, with volume changes of 0.29 to 4.03 m3 detected between visits. The rock displaced from the ribs could not be measured independently of the remote sensing, but a uniform absence of rock movement across large areas of the mine validates the accuracy of the point clouds. A similar test was performed using laser scanning in an underground coal mine, where the displacement was induced by removing material by hand from the ribs. Volume changes as small as 57 cm3, or slightly larger than a golf ball, and as large as 57,549 cm3, were detectable in this environment, despite the change in rib surface reflectance and mine geometry. In addition to the rib displacement, photogrammetry was selected as a tool for monitoring standing supports in underground coal mines. The additional regulatory restrictions of underground coal may preclude the use of laser scanning in these mines where deformation is most likely to occur. The camera used for photogrammetry is ATEX certified as explosion proof and is indicative of the specifications that could be expected in an MSHA approved camera. Three different experiments were performed with this camera, including a laboratory controlled standing support deformation at the MRS and an in-mine time-lapse experiment measuring the response of a wooden crib and steel support to abutment loading. The experiment reconstructing a standing support in the MRS showed a cumulative convergence of 30.93 cm through photogrammetry and 30.48 cm as measured by the system. The standing support monitoring in the underground coal mine environment showed a steel support cumulative convergence of 1.10 cm, a wooden crib cumulative convergence of 0.62 cm, and a measured cumulative convergence on the wooden crib of 0.62 cm. These techniques explored in this report are not intended to supplant, but rather supplement, existing measurement technologies. Both laser scanning and photogrammetry have physical and regulatory limitations in their application to measuring underground mine deformations, however, their ability to provide time-lapse three-dimensional measurements of entire mine sections is a strength difficult to emulate with traditional point measurement techniques. A fast, cost-effective, and practical application of remote sensing to monitoring mine displacements will improve awareness and understanding of rock mass behavior. / Ph. D.

There are two major design problems for upper seam longwall gateroads operating in a multi-seam environment. The first is to determine the location, magnitude and duration of stress transferred from lower seam mines; and the second is to predict the effect of stress transferred from lower seam mines on opening stability. To solve these problems for both longwall and room-and-pillar mines, case study data were collected and analyzed to develop empirical models predicting upper seam damage created by mining activities in the lower seam. Analysis showed vertical movement in the upper seam and roof CMRR (Coal Mine Roof Rating) to be the controlling factors in damage prediction and, therefore, gateroad planning and design. The relationship between the predicted damage rating and the gateroad stability was established and quantified. To simplify the application of design procedures developed for longwall gateroad systems, the criteria were incorporated in a Windows-based, multi-interface software , UGLY (Upperseam Gateroad Longwall Stability). The programming language was Visual Basic, and the program's design capabilities were validated and demonstrated using case study data. / Master of Science